总述:本次共解1题。其中
☆方程1题
〖 1/1方程〗
作业:求方程 2.4*400*10*(1+a%)+2.4*(1+a%)*500*10*(1+20a%) = 21600*(1+20/9*a%) 的解.
题型:方程
解:原方程:| | 12 5 | × | 400 | × | 10 | ( | 1 | + | a% | ) | + | 12 5 | ( | 1 | + | a% | ) | × | 500 | × | 10 | ( | 1 | + | 20 | × | a% | ) | = | 21600 | ( | 1 | + | 20 | ÷ | 9 | × | a% | ) |
| 方程左边 = | 9600 | ( | 1 | + | a% | ) | + | 12000 | ( | 1 | + | a% | ) | ( | 1 | + | 20 | × | a% | ) |
方程化为:
| | 9600 | ( | 1 | + | a% | ) | + | 12000 | ( | 1 | + | a% | ) | ( | 1 | + | 20 | × | a% | ) | = | 21600 | ( | 1 | + | 20 | ÷ | 9 | × | a% | ) |
去掉方程左边的括号:
| 方程左边 = | 9600 | × | 1 | + | 9600 | × | a% | + | 12000 | ( | 1 | + | a% | ) | ( | 1 | + | 20 | × | a% | ) |
| = | 9600 | + | 96 | a | + | 12000 | ( | 1 | + | a% | ) | ( | 1 | + | 20 | × | a% | ) |
| = | 9600 | + | 96 | a | + | 12000 | × | 1 | ( | 1 | + | 20 | × | a% | ) | + | 12000 | × | a% | ( | 1 | + | 20 | × | a% | ) |
| = | 9600 | + | 96 | a | + | 12000 | ( | 1 | + | 20 | × | a% | ) | + | 120 | a | ( | 1 | + | 20 | × | a% | ) |
| = | 9600 | + | 96 | a | + | 12000 | × | 1 | + | 12000 | × | 20 | × | a% | + | 120 | a | ( | 1 | + | 20 | × | a% | ) |
| = | 9600 | + | 96 | a | + | 12000 | + | 2400 | a | + | 120 | a | ( | 1 | + | 20 | × | a% | ) |
| = | 21600 | + | 2496 | a | + | 120 | a | ( | 1 | + | 20 | × | a% | ) |
| = | 21600 | + | 2496 | a | + | 120 | a | × | 1 | + | 120 | a | × | 20 | × | a% |
| = | 21600 | + | 2496 | a | + | 120 | a | + | 24 | a | a |
| = | 21600 | + | 2616 | a | + | 24 | a | a |
方程化为:
| | 21600 | + | 2616 | a | + | 24 | a | a | = | 21600 | ( | 1 | + | 20 | ÷ | 9 | × | a% | ) |
去掉方程右边的括号:
| 方程右边 = | 21600 | × | 1 | + | 21600 | × | 20 | ÷ | 9 | × | a% |
方程化为:
| | 21600 | + | 2616 | a | + | 24 | a | a | = | 21600 | + | 480 | a |
方程化为一般式后,用因式分解法化为:
( a + 89 )( a +0 )=0
由
a + 89 = 0
a + 0 = 0
得:
a1=-89,它是方程的增解。
a2=0
有 2个解。
其中有1个增解,剩下1个实数解。(提示:“增解”是计算机计算产生,但是又不符合该方程式。)
解一元二次方程的详细方法请参阅:《一元二次方程的解法》
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